MESA COUNTY, Colo. (CBS4) – The Mesa County District Attorney said there is no evidence of premeditation in the case of a Colorado mother arrested in the accidental death of her two boys.

“If you look at the definition for criminal negligence, in Colorado, it includes accidents. And I’ve never said this is anything but an accident,” said Mesa County DA Pete Hautzinger.

Heather Jensen will not fight extradition. She told a judge Thursday morning in Lee County that she doesn’t oppose being brought back to Mesa County on Colorado’s Western Slope for legal proceedings. She remains in jail in Fort Myers.

The Mesa County District Attorney’s office filed charges of negligent homicide against Jensen on Wednesday.

Investigators said she left her 2-year-old and 4-year-old son in her SUV on Nov. 27 on a rural road near Powderhorn ski resort while she allegedly smoked pot and had sex with one of two men she was seeing. The boys died of overheating (technically “hyperthermia”).

“I do think when you apply the facts of this case to Colorado law it does amount to criminal negligence to leave children in a car, running, unsupervised and an unaccounted period of time,” said Hautzinger.

Heather Jensen posted photos of William and Tyler on her Facebook page. (credit: Facebook)

“It’s a horrible horrible tragedy. It was not an intentional killing. I filed the charges I think are appropriate and we’ll take it from there,” Hautzinger said.

So far it’s not clear how soon Jensen could be brought back to Colorado.

“As soon as she’s back in my jurisdiction she’ll be advised of the potential charges and we’ll take it from there, but I don’t have a feel for how soon that will be,” said Hautzinger.

The youngest boy, William, died in the vehicle. His brother, Tyler, had also been in the car and ended up being transferred to a hospital in Denver where he died a week later.

Earlier this month the coroner released a report saying the boys’ deaths was accidental, but wrote the following in a report released this week:

“Despite neglect being the direct precipitating factor in the death of the decedent and his sibling, deliberate intent to kill cannot be established with certainty; therefore, the manner of death is classified as accident. The manner of death may be reclassified as homicide if additional information becomes available.”

The specifics of what led to the deaths have been kept under wraps until this week, and it appears Jensen told police different stories about what happened.

Heather Jensen (credit: Facebook)

An arrest affadavit revealed the following timeline of what apparently led to the emergency:

– Jensen was allegedly having an affair with a man named Peter, who moved into her apartment with her boys two days after her husband — the boys’ father Eric — died in a car crash.

– Jensen was also having a sexual relationship with another man, Colten, who she ended up meeting at 4 p.m. on Nov. 27 near Powderhorn with her boys asleep in their car seats. She got in Colton’s truck about an hour later, apparently smoked some marijuana and then turned her car on at 5:15 p.m.

– Jensen returned to the car around 5:40 p.m. after her older boy tried three times to open the door. She gave him her phone to play games with and engaged the child locks on the doors, had sex and was back in her car around 6:20 p.m.

– Jensen sent a text to Peter saying they were having fun playing in the snow at 6:24 p.m.

– She called 911 at 6:29 p.m.

(credit: CBS)

It appears from the document that that the children were in the car for about two hours and 20 minutes total. During that time, it appears that the boys were unattended for about 40 minutes up until the 911 call.

Police did some testing at the scene and said the heat in the SUV could have reached 136 degrees if the heat was on.

“In all candor, I was leaning toward filing criminal charges weeks ago but then the coroners office came out with a determination they were calling it that the deaths were accidental,” said Hautzinger. “That caused me to take a step back and re-evaluate and be as careful as I could.”

Hautzinger said he’s found only three other hyperthermia court cases in the past 15 years.

“Accident means something different in a forensic pathology context vs. a criminal context,” said Hautzinger. “Who among us would reasonably expect a car heater at a ski area at that altitude in November to cause something like this. That’s a big part of why I took so long on my decision. I wanted to research hyperthermia as thoroughly as I could.”

Rodger Mathena, Eric’s brother and the boys’ uncle, told CBS4 in Littleton on Wednesday that he expected Jensen would be arrested.

“I knew it was going to happen eventually,” he said.

Jessica Howard, a family friend, also told CBS4 she remains deeply upset about the case.

“As a mom I can not imagine just to be one car length away and your children are laying there … and getting pleasure is more important,” Howard said. “It makes me sick.”